Method for producing a polymer-improved pipe element

This application is a 35 U.S.C. § 371 application of International Application No. PCT/EP2021/087499, filed Dec. 23, 2021, which claims the benefit of European Application No. 20216864.7, filed Dec. 23, 2020, each of which is incorporated by reference in its entirety.

The invention relates to a method for the automated or partially automated production of a polymer-enhanced pipe element using pipe sections subject to tolerances.

The production of polymer-enhanced pipe elements for fire extinguishing systems is known, for example, from EP 2623163 B1, EP 2766653 B1 and WO 2020/002502 A1. The possibility of applying to the pipe a highly corrosion-inhibiting coating with long-term resistance by means of polymer enhancement is gaining in importance especially in areas of application in which it is increasingly important to have long-term resistance to corrosion for safety considerations. One example of such applications which may be highlighted is the use of polymer-enhanced pipe elements in fire extinguishing systems, but the uses of such polymer-enhanced pipe elements in industrial plants with corrosion-promoting media which have to be transported, or in corrosion-promoting environments, such as, inter alia, fluid line systems in maritime environments, are also increasingly relevant fields of application.

It is known that it is important for successful coating in polymer enhancement to avoid potential subsequent corrosion foci in pipe production. It is also known, from the abovementioned documents for example, that pipe elements which consist of a plurality of pipe sections, such as, for example, main bodies and stubs attached laterally to them, are connected to one another by welding, wherein it is possible for such corrosion foci to be formed or for the coating to be formed incorrectly due to surface artifacts in the region of the weld seam as a result of impurities, deviations in shape and other aspects. It is furthermore known that, given complete root fusion in the welding process, most of such problem areas on the inside of the pipe can be eliminated quite reliably in the subsequent pickling process.

In practice, it has been found that the production of a pipe element from a plurality of pipe sections by means of welding faces particular challenges when use is made of pipes which are subject to tolerances and which can differ from pipe to pipe in terms of their wall thickness, roundness and pipe bending. However, the use of such pipes is desirable for economic reasons and especially for applications in which very large quantities, i.e. pipe lengths, have to be processed.

It has therefore been an object of the invention to specify a method of the type designated at the outset in which the disadvantages described above are overcome as far as possible. In particular, it was an object of the invention to provide a method of the type designated at the outset which permits economically advantageous production of pipe elements without impairing the quality of the surface coating by means of polymer enhancement.

The invention achieves the object on which it is based, in a method of the type designated at the outset, in that it has the following steps:

Pipes subject to tolerances are understood to mean, for example, pipes where the deviations in the outside diameter were up to +/−1%, which would correspond to a tolerance band of approximately 4 mm at a nominal diameter of DN 200. The tolerance of the pipe elements with respect to the wall thickness can be +/−10% in the case of pipes subject to tolerances in the sense according to the invention, and therefore the inner contour can also have a tolerance band of up to 0.4 mm in the case of a pipe of diameter DN 200. In the case of pipes subject to tolerances, the geometrical accuracy can be up to 2% and the deviation of the straightness can be 3 mm per meter.

The invention makes use of the realization that, by determining the spatial penetration curve on the basis of the three-dimensional shape of both pipe sections, it is possible to prepare a reference set for the shape to be introduced into both pipe sections, which set ensures exact shape-matching of the first and second pipe sections in their connecting region, irrespective of the tolerance-induced shape deviations that occur in practice.

With the invention, it is possible to process pipes which are already dimensioned and toleranced quite exactly ex works, but also pipes which have the tolerance ranges described above, or have even greater deviations than these. In other words, the common spatial penetration curve makes it possible to introduce the exact outer shape of the first pipe section as a cut edge into the second pipe section if the second pipe section is a stub and the first pipe section is an elongate base pipe. Conversely, the common penetration curve makes it possible to introduce the exact shape of the second pipe section as a cutout into the first pipe section.

The step of welding the first and second pipe sections is preferably carried out in a single continuous movement. This means that the welding device is applied and traverses the common spatial penetration curve in one pass until the weld seam is complete, without temporarily disengaging. The welding device preferably disengages only when the application point has been reached again and when, in particular, the root formations of the weld seam are connected to one another. A desired weld seam quality, for example class B according to DIN EN ISO 5817:2014 or analogous other standards, is thereby achieved by a reliable process. The procedure is made possible by the determination and subsequent use of the common spatial penetration curve. As a result, the weld seam formed in a single continuous pass is of more regular configuration than weld seams that are produced manually or semi-automatically can be, whereby in turn the ability of the pipe element to form a low-defect or defect-free surface coating by means of polymer enhancement is improved.

Preferred embodiments of the method according to the invention are described in the claims and in the following explanations.

In a first development of the method, the step of determining the three-dimensional shapes comprises providing an idealized model of the first pipe section and an idealized model of the second pipe section, and determining deviations of the detected shape of the pipe sections from a respective model. The idealized models are, for example, cylinders with the predetermined theoretical outside diameters of the pipe sections. The outside diameters are the quantity which is also recorded metrologically. In other words, it is the actual deviations of the pipe sections from their desired geometry which are detected in this method step.

In a development of the method, the step of determining the spatial penetration curve comprises providing or generating an idealized penetration curve of the idealized models, and generating the spatial penetration curve by applying the deviations of the three-dimensional shape to the idealized penetration curve.

In an alternative preferred embodiment, the step of determining the three-dimensional shapes comprises determining families of points for both pipe sections, wherein the families of points are situated on the respective surface of the pipe sections in the respective connecting region and characterize the three-dimensional shape of the pipe sections in the connecting regions, and wherein the step of determining the spatial penetration curve preferably further comprises forming the spatial penetration curve from the intersection of the families of points. In other words, according to this variant, those points are found which have the same coordinates in both families of points. If the two detection steps are not carried out in the same coordinate system, the families of points are preferably transposed into a common coordinate system.

The advantage of the invention is particularly apparent here: By means of the common spatial penetration curve, it is possible, in a partially automated or automated method, to carry out all the steps of the mechanical processing of the pipe sections, such as their positioning in the installation, the generation of the edges in the connecting regions for the subsequent welding process, the cleaning and dressing of the cut surfaces produced, and the welding itself, in each case on exactly the same path as a function of the spatial penetration curve. As a result, sources of error which could be associated with inaccurate positioning or could result from unforeseen shaping of the pipe sections are very largely ruled out.

The method is preferably developed in that it comprises the step of clamping the first pipe section by means of a clamping device, preferably in such a way that the first pipe section is received so as to be rotatable about an axis of rotation of the clamping device. In other words, the first pipe section is preferably clamped in such a way as to be rotatable about a defined instantaneous pole, which would represent the theoretical center of the pipe if this corresponded to an idealized cylinder. The rotary function can be implemented, for example, by rotating the entire clamping device about this pipe center axis, which also forms what is referred to as the tool center point (TCP) of the common coordinate system, or by rotating only the first pipe section. In principle, the method according to the invention can also be carried out if the pipe section is not rotatable.

As a further preference, the method comprises the steps of picking up the second pipe section by means of a handling device, in particular a handling robot, and positioning the second pipe section in a fixed position relative to the first pipe section. In a first preferred variant, the handling device holds the second pipe section continuously in the fixed position relative to the first pipe section until welding has been carried out. In a preferred second alternative, the second pipe section is held by means of the handling device only until it has been mechanically fixed in some other way relative to the first pipe section, for example by means of tack welding.

In a further preferred embodiment of the method, the step of generating the edge surfaces comprises cutting peripheral edge surfaces on the first and second pipe sections, preferably by means of plasma cutting, wherein edge surfaces on the first and second pipe sections are preferably cut with an inner edge and an outer edge in each case.

As a further preference, the edge surfaces on the first and second pipe sections are cleaned before the welding step.

As a further preference, the edge surface to be produced on the first pipe section is at a distance from the ends thereof and defines a cutout through the wall of the first pipe section, and the generating edge surface on the second pipe section is formed on an end of the second pipe section. In other words, the first pipe section is a base pipe having a lateral aperture at a distance from the end, and the second pipe section is a stub which is configured for lateral attachment to the first pipe section and is aligned flush with this cutout.

The first and second pipe sections are preferably aligned at an angle of 90°+/−0° to 5° to one another.

Alternatively or additionally, the first and second pipe sections are preferably aligned in such a way that they rest against each other without gaps or that there is a joining gap of 0.2 mm or less.

The method preferably further comprises the step, for the step of providing the first and second pipe sections, of scanning the marking of the pipe sections to be processed. Scanning corresponding markings in pipe sections makes it possible to implement acquisition of the (theoretical) nominal diameters, wall thicknesses etc. of the pipe sections to be processed for the automation of welding. This acquired information can be used, for example, for the automatic setup of the handling devices, the clamping device and so on.

In a further preferred embodiment, the step of welding the first and second pipe sections comprises welding the pipe sections along the penetration curve; forming a fully encircling weld seam which has a root extending to the inside of the pipe sections, wherein the root of the weld seam has a thickness such that at least one of the inner edges, and preferably both inner edges, is or are completely fused by the root, wherein the root of the weld seam completely fuses the inner edge of one of the pipe sections, and the remaining inner edge of the other pipe section is at a distance from the weld seam by a predetermined maximum value in the radial direction, wherein in particular the predetermined maximum value, a) if the first and second pipe sections have the same wall thickness, is less than or equal to half of a wall thickness of the pipe sections, particularly preferably less than or equal to one fourth of the wall thickness of the pipe sections, or b) if the first and second pipe sections have different wall thicknesses, is less than or equal to a difference between the wall thicknesses of the pipe sections, particularly preferably less than or equal to one half of the difference in the wall thickness of the pipe sections.

The method according to the invention preferably further comprises the step of applying a polymer-based layer to the inside of the pipe element, wherein the polymer-based layer completely covers the inside of the pipe element, wherein the application of the polymer-based layer is preferably accomplished by means of autodeposition, as a further preference by means of dipping the pipe element in a dip tank which contains an appropriate coating agent, in particular a polymer-based chemical autodeposition material. This method step, in which the polymer enhancement is added to the pipe, can be used successfully with various chemical autodeposition materials, for example. For example, epoxy-acrylic urethane coatings, such as Bonderite M-PP 930, have proven to be suitable in the past. The properties of these autodeposition materials are known, and these materials can be well managed in the coating process, even on an industrial scale. The autodeposition coating is described, for example, in the documents designated at the outset, the content of which is fully incorporated here.

The invention has been described above in a first aspect with reference to the method explained. In a further aspect, the invention further relates to an apparatus for the automated or partially automated production of a polymer-enhanced pipe element using pipe sections subject to tolerances, wherein the pipe sections each have a connecting region, which is provided for connection to the respective other pipe section.

The invention achieves the object on which it is based by virtue of the fact that the apparatus has at least one detection device for detecting a three-dimensional shape in each case in the connecting regions, a computing unit, which is configured to determine a spatial penetration curve as a function of a superposition of the detected three-dimensional shapes, and to determine cut contours in the connecting regions of the first and second pipe sections as a function of the penetration curve, a cutting device for producing edge surfaces in the connecting regions of the first and second pipe sections along the respective cut contours, and a welding device, which is configured to weld the first and second pipe sections to one another along the mutually aligned edge surfaces along the determined spatial penetration curve.

The apparatus makes use of the same advantages and preferred embodiments as the method according to the invention according to the first aspect, and therefore reference is made in this regard to the above statements in order to avoid repetitions. Preferred embodiments of the method are at the same time preferred embodiments of the apparatus and vice versa.

In a preferred development of the apparatus, the apparatus has a device for collecting welding, cutting-jet or other artifacts which are hurled away by the welding or cutting jet from the point of processing, for example welding spatter, displaced liquid metal from the process of plasma cutting, or flying chips, on the inside of the first and/or second pipe sections, which device is designed to be positioned in the connecting regions of the first and/or second pipe sections before welding, particularly preferably substantially opposite the welding or cutting location. This reduces or prevents damage to and contamination of the inner surface and thus also reduces the risk of impairment of the surface quality in the interior of the pipe.

For this purpose, the device preferably has a collecting container which is matched to the inside diameter of the first pipe section and is configured to collect as many of the above-mentioned artifacts as possible. The collection of the artifacts, which according to the invention is likewise carried out as part of a partially automated or automated process, is described in more detail, for example, in WO 2020/002486A1, the content of which is fully incorporated here.

In a preferred embodiment, the apparatus according to the invention has a clamping device for the first pipe section, and a handling device, in particular a handling robot, for the second pipe section.

The clamping device preferably has at least one clamping means, preferably a plurality of clamping means, and is configured to rotate the first pipe section about an axis of rotation, wherein the axis of rotation of the clamping device in its clamping position preferably runs through the origin of the coordinate system of the common spatial penetration curve, or wherein the common spatial penetration curve is transposed, if necessary, into the coordinate system, one axis of which represents the axis of rotation. If the first pipe section has already been clamped before the three-dimensional shape has been detected, the detection and thus also the determination of the common penetration curve can be performed directly in the correct coordinate system, making it possible to omit a transposition.

In a further preferred embodiment, the clamping means comprises a clamping center, which defines the axis of rotation of the clamping device. In further preferred embodiments, the above-described clamping means is a first clamping means and the clamping device further has a second clamping means, which is arranged at an axial distance from the first clamping means along the axis of rotation, wherein the clamping device is configured to clamp the first pipe section on both sides of the connecting region by means of the clamping means. In this case, it is basically advantageous to choose a distance between the clamping means which is as small as possible.

As a particular preference, the clamping means can be moved relative to one another in the direction of the axis of rotation, so that the clamping distance between the clamping means can be set as a function of the diameter of the second pipe section. The smaller the selected distance between the clamping means can be, the smaller is a wobbling movement of the first pipe section during its rotation. The wobbling movement arises inevitably because of a radial offset between the axis of rotation of the clamping device and the center of mass of the first pipe section, because the pipe section does not have an idealized cylindrical shape but is also subject to tolerances with regard to its straightness.

In addition, the pipe section is preferably clamped in accordance with the expected deformation of the pipe section as a result of the impending introduction of heat. The influence of the thermally induced deformation on the calculated welding path is thereby reduced.

This means that the deflection of the surface of the first pipe section is smaller in absolute terms, even in the case of curved pipe sections which do not extend in a straight line, and this facilitates the positional tracking of the handling device which is to carry out the welding operation.

In a further preferred embodiment, the clamping means is/are designed to be open on one side and is/are configured to receive and clamp the first pipe section from above. By designing the clamping means to be open on one side, two advantages are simultaneously achieved: On the one hand, the pipe elements can be inserted into the clamping device from above, making handling in automated production significantly easier and reducing the space requirement. On the other hand, the open region of the clamping device at the top can provide better access to the connecting section of the pipe sections for the handling device or devices.

In a further preferred embodiment, the first and/or second clamping means is/are configured to fix the pipe section, and the clamping device or the clamping means is or are configured to pivot the clamping means in such a way that the first pipe section rotates about the axis of rotation of the clamping device. It may be advantageous to allow the entire clamping device to rotate and to fix the clamping means relative to the clamping device.

In a preferred embodiment, the clamping means are designed as centrally clamping clamping devices, particularly preferably as steady rests.

In a further preferred embodiment, the clamping device has an arcuate guide along which the clamping means is movably received, wherein the guide is aligned concentrically relative to the axis of rotation and is configured to guide the clamping means around the axis of rotation. When using a plurality of clamping means, preferably at least one, preferably a plurality or all of the clamping means is or are arranged so as to be movable about the axis of rotation by means of a separate guide of this type.

In a further preferred embodiment, the handling device is a first handling device, and the apparatus further has a second handling device, in particular designed as a handling robot, which has a receptacle for various processing attachments. The attachments—also referred to as working heads—preferably comprise one or more of the following: to form the cutting device, a cutting torch, laser, water jet or a machining head for machining (including finish-machining of the cut edges, in particular for milling); as a cleaning device, an attachment for hammering, blasting, scraping, brushing or plasma blasting; to form the detection device, a mechanical surface probe, a dynamic pressure sensor, a plasma surface sensor, one or more optical sensors; to form the welding device, a welding head, for example a MIG, MAG or TIG welding head, or, in the case of brazing instead of welding, a brazing device.

The attachments preferably each have an assembly interface of corresponding design to the receptacle of the handling device, and have a point of action (tool center point). In the case of a marking pen, for example, the point of action is the marking tip, in the case of a welding attachment the welding point, etc. As a particular preference, the point of action in the case of all the attachments is positioned identically relative to their assembly interface. This has the effect that, when guided along the same path by the handling device, the tools perform exactly the same movement through space with their point of action. This, in turn, has the effect that a plurality of tools, for example the measuring attachment, the cutting torch attachment and/or the welding attachment, can be guided by means of a single path. It is not necessary to program or calculate a separate path for each tool. In this preferred embodiment, therefore, it is only necessary to calculate the spatial penetration curve once, and this can then be used for all working steps despite any tool changes. As a result, considerable computing and time resources can be saved and manufacturing tolerances can be reduced at the same time.

The apparatus preferably has an electronic machine controller, which is connected in a signal-transmitting manner to the detection device, the computing unit, the cutting device, the welding device, and preferably one, more or all of the clamping device, the first and/or the second handling device and is configured to carry out the method according to any of the preferred embodiments described above.

The machine controller can be designed as a master control device, which communicates with one, several or all of the aforementioned devices in a signal-transmitting manner and controls them, or can have one or several sub-control units, which are each assigned to the above-described devices, and each carry out dedicated control of the respective units.

The program architecture will be adapted depending on the application and on the machine concepts available to the respective plant operators, it being possible, for example, for the electronic machine controller, as a master controller, to control two mechanical systems, each with a CNC control system.

The machine controller preferably has a higher-level programmable logic controller (PLC), as well as a human-machine interface, and further preferably functional units such as an order management unit and a control unit for the peripheral devices of the apparatus. The two mechanical systems each have a dedicated CNC control system and a handling device designed as a six-axis robot. The first mechanical system is preferably responsible for the first pipe section and the second mechanical system is responsible for the second pipe section.

The first mechanical system preferably has a positioning device for the pipe, which has the clamping device, as well as a sensor system for surface measurement, which has the detection device. Furthermore, the first mechanical system has processing hardware for cutting the first pipe section and for welding the pipe connection between the two pipe sections, both of which are preferably operated by means of the handling device.

The second mechanical system preferably likewise has a handling device designed as a six-axis robot, and is responsible for the handling and positioning of the second pipe section, preferably a pipe stub. The second mechanical system also preferably has a sensor system for surface measurement, which represents the detection device, as well as the hardware for cutting the second pipe section to shape and for positioning the stub for joining or for joining itself, if necessary.

The invention has been described above on the basis of the first and second aspects with reference to the method according to the invention and the apparatus according to the invention. The invention further relates to a computer program product, comprising commands which, when the program is executed by a computer, preferably by the machine controller of the apparatus, cause it then to carry out the steps of the method according to any one of the preferred embodiments described above.